1. Technical Field of the Invention
This invention relates generally to manufacturing and testing of liquid crystal on semiconductor display devices, and more specifically to wafer-level testing and device structures that support such.
2. Background Art
Liquid crystal on silicon (LCOS) display devices include an array of display pixels fabricated on a silicon or other semiconductor substrate with associated control circuitry, and a quantity of liquid crystal material encapsulated overlying the display pixel array. When appropriate electrical signals are applied to the various pixels, they alter the transparency or polarization or reflectivity of the liquid crystal material which overlies their respective areas.
Unfortunately, at present, the LCOS chips must be fully fabricated and assembled before they can be tested. Of any given semiconductor wafer, there will typically be a numberxe2x80x94sometimes a large numberxe2x80x94of semiconductor dice which are defective and must be rejected. Overall costs are increased, materials are wasted, and factory output is reduced, by the ultimately unnecessary completion and assembly of these defective devices.
Also, on present LCOS devices, the wire bond attach pads are located on the same side of the die as the liquid crystal display structures. This makes testing difficult, and makes test head devices complicated and difficult to make and use.
What is needed, then, is a way to perform wafer-level testing of LCOS devices before their final fabrication steps and their assembly.